The classification of earthworms is a subject that can be approached from several different directions. Classically, one would endeavor to classify a group of creatures with respect to their shared phylogeny; that is, the shared evolutionary ancestry of the group of species in question would dictate their overarching classificatory structure. In the case of earthworms, however, researchers have instead opted to adopt a lexicon based more on earthworms’ functional-ecological roles than on their genetic heritage (although we must note that the two often, though not always, can be found to coincide). To that end, we present a brief overview of the three principal categories of earthworms that constitute the dominant classificatory paradigm of today’s researchers: epigeic, endogeic, and anecic. These categories are closely related to earthworms’ habits within soil, as explained forthwith.